Paint system

ABSTRACT

A paint system containing at least one pump  150  and at least one paint mixing vessel  160.  At least one return line  46  functions to route paint from the paint system back into the paint mixing vessel from whence it was drawn. At least one eductor  522  fluidly communicates with a respective paint mixing vessel  160  and a respective return line  46  whereby during operation of the paint system, as paint traverses through return line  46  and into eductor  577,  paint is drawn from the respective paint mixing vessel  160  thereby mixing the paint drawn from the vessel with the paint in the return line  46.

BACKGROUND OF THE INVENTION

In large paint finishing facilities, paint materials are delivered toapplication points through a network of distribution pipes. The paint isgenerally pumped through the pipes from a central location (paint mixroom or paint kitchen) designed for handling and storage of flammableand combustible liquids (e.g., solvent-based paints and/or water-basedpaints.) Various types of pumps are used for this purpose. The paintmaterials are adjusted to proper viscosity for application and containedin tanks connected to the pumps.

The paint is continually circulated between the mix room and theapplication points to prevent settling of pigments and metallicparticles or similar appearance enhancers (mica, etc.) in thedistribution pipes, which would result in sub-standard finish appearanceon the painted product. Paint tank agitation methods commonly used tomaintain mixing of the paint within the paint mixing vessel may employ aseries of paddles, propeller, or serrated disks (FIGS. 2-5) connected toa drive shaft which, in turn, is connected to a gear motor or to a gearreducer and motor. In high volume production facilities such asautomotive or similar production, electric motors ranging in horsepowerfrom ½ to ten HP, depending on the mix tank size and paint propertiesare used to drive the agitators at the required speed.

The components of conventional paint agitation systems are generallybulky and expensive, and frequent, complex, and expensive maintenanceprocedures may be required to maintain these components in workingorder. Furthermore, the drive mechanism or motor for each agitatorincreases the cost of operating the paint system as well as increasingthe maintenance requirements for the overall system. In particular,systems with multiple paint colors require an agitation means for eachpaint pot of the system. As the number of paint pots increase within agiven system, the operating cost increases accordingly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a paint circulating system in accordancewith the present invention;

FIG. 2 is a cross-sectional view of a mix tank and an associated paintagitation system in FIG. 2 is a cross-sectional view of a mix tank andan associated paint agitation system in accordance with the presentinvention; and

FIG. 2A is a cross-sectional plan view of the mix tank shown in FIG. 2;

FIG. 3 is a cross-sectional view of an alternative embodiment of the mixtank and associated paint agitation system shown in FIG. 2; and

FIG. 3A is a cross-sectional plan view of the mix tank shown in FIG. 3.

FIGS. 4 and 5, when combined, disclose an exemplary paint system inaccordance with the present invention.

FIG. 6 is a view of the system of FIGS. 4 and 5 in the paint recoverymode.

FIG. 7 is a view of the system of FIGS. 4 and 5 in the line flush mode;

FIG. 8 is a view of the spray gun line flush fluid circuit; and

FIG. 9 is a view of the pump flush fluid circuit.

FIGS. 10 and 11, when combined, is a view of a second paint line withina paint system of the present invention, thereby illustrating aplurality of paint lines within a paint system, particularly whencombined with FIGS. 4 and 5.

DETAILED DESCRIPTION

FIG. 1 shows a schematic of a paint circulating system 510 incorporatinga paint agitation system 520 in accordance with the present invention.

Paint circulating system 510 includes a paint mix tank 518 for storingand mixing of the paint, a paint application area 512 (for example, apaint spray booth), at least one paint supply line 514 for conveyingpaint from mix tank 518 to paint application area 512, and at least onepaint recovery or return line 516 for conveying paint from applicationarea 512 to mix tank 518. Circulation of paint between mix tank 518 andapplication area 512 is provided and managed by a paint flow regulationsystem, generally designated 515.

Paint flow regulation system 515 comprises an arrangement of knownelements, such as pumps, valves, pressure regulators, compressed airlines, and other components necessary for regulating flow of the paintbetween a paint reservoir (such as mix tank 518 of the presentinvention) and paint application area 512, in accordance with designrequirements of the paint system. One example of such a flow regulationsystem is disclosed in U.S. Pat. No. 5,389,149, incorporated herein byreference. Numerous other known configurations of flow regulation systemare possible and would be suitable for regulating paint flow in thepaint circulating system described herein, depending on designrequirements.

Paint recovery line 516 provides a conduit for conveying unused paintfrom paint application area 512 back to mix tank 518. In the embodimentshown in FIGS. 2 and 2A, one or more flexible branch lines 516 b extendfrom a main line 516 a. Branch lines 516 b are fluidly coupled, viasuitable piping or tubing, to eductors 522, described in greater detailbelow. The use of multiple branch lines 516 b extending from mainrecovery line 516 a enables multiple associated eductors 522 to besupplied with paint from the main return line. Because eductors 522 arefluidly coupled to paint recovery line 516, the pumps in paint flowregulation system 515 used to circulate the paint through the paintsystem can also be used to supply paint to the eductors.

FIG. 2 shows a cross-sectional view of a mix tank and an associatedpaint agitation system in accordance with the present invention. Mixtank 518 is provided for storing and mixing paint compounds. Mix tankmay include one or more baffles 519 for disrupting paint flow patternswithin tank 518, thereby increasing turbulence within the stored paint,in a manner known in the art.

The present invention uses the circulated paint returning to mix tank518 to agitate the tank contents, using Coanda or Venturi effecteductors to amplify the volume of the returning paint to maintainrequired agitation of the tank contents, thereby eliminating or reducingthe need for separate agitation devices. Referring again to FIG. 2, oneor more eductors 522 are positioned proximate the bottom of mix tank 518where settling of the paint constituents is most likely to occur.However, eductors 522 may alternatively be positioned at any suitablelevel within mix tank 518. In addition, multiple eductors 522 may bepositioned at different levels within mix tank 518, depending upon suchfactors as the tank geometry and the mixing requirements of a particularpaint composition.

The design and positioning of eductors 522 are optimized to produce ahigh turbulence in mixing tank 518 to prevent settling of pigments andmetallic particles or similar appearance enhancers. Eductors 522 areknown liquid eductors for agitating chemicals in tanks. One example of asuitable liquid eductor is manufactured by Fox Valve Development Corp.of Dover, N.J. In a Venturi-type eductor, for example, the paint isforced through a narrow or restricted area in the eductor, resulting inan increase in the speed of paint flow. The increased speed results in areduction in pressure adjacent the accelerated fluid flow. This causesair to be pushed into the lower pressure regions, thereby injecting airinto the paint stream. By injecting air into the returning paint stream,the volume of the returning paint stream is amplified, helping tomaintain required agitation of the mix tank contents. In this manner,eductors 522 are effective for maintaining a high liquid turbulence inmix tank 518 to prevent settling of pigments and metallic particles orsimilar appearance enhancers.

In certain applications, a paint mixture having highly pigmentedconstituents and dense settling characteristics may need supplementalagitation to overcome settling. Also, because of variable productionrequirements and variables that exist in the operation of paint mixfacilities, it may be necessary to provide additional, mechanicalagitation of select tanks. Thus, in an alternative embodiment of thepaint circulating system (shown in FIGS. 3 and 3A), a conventionalagitation system may be incorporated into paint agitation system 520 toaugment the mixing effects of eductors 522. The conventional agitationsystem may include an agitator drive unit 524 suspended from a loadbalancer 530, and an associated mechanical agitator 526 including amixing paddle 526 a. Agitator 526 and drive unit 524 may be fitted withcomplementary quick-disconnect features to enable drive unit 524 to bequickly disconnected from a first mix tank and reconnected to anothermix tank having a similar design, as the need arises.

The apparatus and principles set forth above may be applied to anysuitable paint reservoir to provide needed agitation of the paintmixture.

The present invention offers several advantages. Use of eductors as setforth herein may obviate the need for conventional agitation systems.Thus, the present invention may enable the elimination (or a substantialreduction in the number) of expensive conventional agitation systemcomponents, such as explosion-proof electric agitator motors,explosion-proof wiring, and agitator motor starters and controls.Elimination or reduction of these components reduces agitation systemmaintenance time and associated costs, system power consumption, andsystem power feeds.

Exemplary Paint System

Various paint systems are known in the art. In accordance with thepresent invention, and for example only, a description of a paint systemincorporating the agitation means or mechanism of the present inventionis described below.

Referring to FIGS. 4 and 5 of the drawings, a paint system 20, inaccordance with an exemplary constructed embodiment of the presentinvention, comprises a paint booth 22 that accommodates one or morevehicle bodies 24. Conventionally, the vehicle body 24 moves through thepaint booth 22 on a skid 26. The essence of the instant invention is apaint system 20 that enables the vehicle 24 to be painted with a customcolor in an economical manner from the standpoint of both time and paintutilization.

The paint system 20 comprises a plurality of color changers 30 through44 that are connected, in series relationship, by, for example, fourteen(14) discrete paint lines 46 through 59. A paint line is provided foreach color accommodated by the system. Thus, in the disclosed andconstructed embodiment of the invention, fourteen (14) colors can beaccommodated by the system 20. However, for purposes of clarity, onlyone line 46 is shown connecting the color changers 30 through 44 inseries.

The color changers 30 through 44 are provided with solenoid valve panels60 through 74, respectively, located exteriorly of the spray booth 22which, in turn, are controlled by push buttons on a like plurality ofpush button panels 76 through 90, respectively, located internally ofthe spray booth 22.

Each of the color changers 30 through 44 services a spray gun 100through 114, respectively, through discrete flexible paint supply lines120 through 134, respectively.

Paint is supplied to the system 20 through, for example, the line 46from a pump 150. It is to be understood that each of the paint lines 46through 59 is supplied by a separate pump. Only the pump 150, paint line46 and their associated supply and control system is discussed hereinfor purposes of clarity.

The pump 150 is energized by compressed air supplied thereto from a line152 through a solenoid valve 154, pressure regulator 156, and flexibleair line 158. Paint is supplied to the pump 150 from a paint pot 160 of,for example, 10 gallon capacity, through a ball valve 162 and flexibleline 164. The pump 150 supplies paint under pressure to the line 46through a check valve 166, flexible paint line 168, ball valve 170, andsolenoid valve 172.

Paint is returned through a return portion of line 46 from the colorchangers 30 through 44, through a ball valve 180, back pressureregulator 182, flow meter 184, flexible paint return line 186, and ballvalve 188 to the paint pot 160. The diaphragm of the back pressureregulator 182 is loaded by air pressure from the air line 152 through aregulator 190 and solenoid valve 192.

The system 20 is flushed by aerated solvent or foam produced in aturbulator 200. Aerated solvent flows from the turbulator 200 under thecontrol of solenoid valves 230 and 232 for the solvent, and solenoidvalves 234 and 236 for the air. The solvent flows through a line 238 toa bank of solenoid valves 240 through 266 and through a line 270 to abank of solenoid valves 272 through 296, the function of which will bedescribed hereinafter.

Operation

The paint system 20 is conditioned for painting of a given color byconnecting the paint supply hose 164 between the pump 150 and the paintsupply solenoid 162 of a paint pot 160, containing a desired color. Thepaint return hose 186 is then connected from the flow meter 184 to thepaint return ball valve 188 on the paint pot 160. The paint pot valves162 and 188 are then opened.

The system 20 is electronically conditioned for start by entering avehicle number, a paint code number, and paint line number into aconventional process control computer (PC). As a vehicle 24 enters thespray booth 22 a conventional encoder (EC) transmits vehicle position tothe control computer. The computer will search its memory for theappropriate paint which has previously been loaded into a specific paintpot 160 of the paint system 20. When the paint number is found, thecomputer (PC) energizes the pump 150 and appropriate push button lightsat each of the paint station push button consoles 76 through 90. Paintcirculates continuously in line 46 through the color changers 30 through44. In the example illustrated in the drawings, the push buttons at eachconsole 76 through 90 would be lit that control the paint line 46. Whenthe operator pushes any lighted push button at any console 76 through90, paint flows from the associated color changer 30 through 44,respectively, to its associated spray gun. It is to be noted that in theexample, only the lighted push buttons controlling line 46 can beactivated.

After a predetermined spraying interval, the painter can either energizestop buttons on his associated control console 76 through 90 or thetracking logic in the encoder (EC) and computer (PC) shuts off the colorvalves controlling line 46 in the color changers 30 and 44.

Spray Gun Line Flush

As best seen in FIG. 4, after a vehicle 24 passes a particular colorchanger 30 through 44, its associated spray gun line 120 through 134,respectively, is flushed. Flushing is initiated by first closing thecolor valve in a color changer 30 through 44 by pushing an appropriatepush button on the corresponding color console 76 through 90. Thepainter then disengages an associated spray gun 100 through 114 from agun line 120 through 134 and attaches the line 120 through 134 to anassociated solvent flush connector 300 through 314, respectively. All ofthe connectors 300 through 314 are connected to a common solvent returnline 316 thence to a solvent collection tank 318.

As shown in FIG. 4, the spray gun 100 has been detached from the spraygun line 120 and the line 120 has been reattached to the connector 300of the solvent return line 316. The operator then presses a purge pushbutton on the console 76 which automatically initiates a cleaning cycleof the color changer 30 and spray gun hose 120 by alternately openingthe solvent and air solenoids of the color changers. The opening,closing and time duration sequence is controlled by the controlcomputer. Solvent and air flows through the color changer 30 and line120 for return to the tank 318. The lines 120 through 134 are flushedsuccessively as the vehicle 24 moves through the spray booth 22.

Paint Recovery

As best seen in FIG. 2, after a vehicle 24 has passed through the booth22 and there is no future requirement for the color, as dictated by thecontrol computer (not shown), the paint line, for example paint line 46,is purged of paint. The control computer terminates the flow of paint byshutting off the pump 150 and then opening a paint blowdown valve 400 inair line 152 and closing valve 192 which fully opens the back pressurevalve 182 so as to blow the paint through the line 46 back to the paintpot 160.

Line Flushing

After the paint line has been cleared of paint, and as seen in FIG. 3,the operator disconnects the paint inlet hose 186 from the paint pot 160and connects it to a solvent connection 410. He then opens solvent andair line valves 236 and 232 so as to initiate foamed solvent flowthrough line 238, valve 252, lines 46 and 186 to tank 220. After apredetermined period the solvent valve 232 is closed to initiate flow ofcompressed air only to effect compressed air blowdown.

Pump Flushing

As seen in FIG. 5, flushing of the pump 150 is initiated bydisconnecting the pump inlet hose 164 from the paint pot 160 andconnecting it to a solvent connection 404. A pump flush control is thenenergized opening the air and solvent valves 234 and 230, respectively,in the turbulator 200 and starting the pump 150. Solvent is pumpedthrough the line 270, valve 284, line 164, pump 150, and line 168 to thetank 220. The solvent valve 230 is closed after a set period andcompressed air only flows through the pump 150 effecting final blowdown.

In accordance with the present invention, at least one eductor 522 ispositioned in line with the paint return line 46, and also in fluidcommunication with the paint mixing vessel 160. As paint fluid flowsthrough line 46 it necessarily draws paint from the paint pot 160 andthen directs the fluid into the paint pot 160 as determined by designcriteria. For example, the fluid flowing through paint return line 46may be directed to the bottom of the paint pot 160 thereby providing anaggressive agitation of the paint within paint pot 160. It will beappreciated that each paint return line associated with a given colormay contain an eductor/mixer 522 if desired thereby decreasing theoverall energy requirements of the paint system. Stated another way, inoperation, a paint system of the present invention contains at least onepaint pot, at least one pump circulating at least one paint stream drawnfrom the at least one paint pot, and at least one eductor in fluidcommunication with both the at least one pump and the at least one paintpot. It will be further appreciated that FIGS. 10 and 11 illustrate asecond paint stream line 47 being circulated to a second paint pot 160B,whereby a second pump 150B circulates the second paint stream 47 therebyestablishing fluid communication between a second eductor 522B and thesecond paint pot 160B.

In further accordance with the present invention and with thedescription given above, a method of mixing paint within a paint vesselis characterized by first providing a paint source within a mixingvessel, then circulating or pumping a paint stream, then returning thepaint stream through an eductor in fluid communication with the mixingvessel to draw paint from the mixing vessel, then returning the paintstream and the drawn paint to the mixing vessel. It should beappreciated that a paint system an a method of mixing a plurality ofpaint streams within the paint system is defined as containing aplurality of paint streams may be independently pumped from acorresponding plurality of paint mixing vessels, whereby each of saidplurality of paint streams is routed through one of a correspondingplurality of eductors by pumping said paint stream through one of acorresponding plurality of pumps. Accordingly, a plurality of paintlines is provided wherein each paint line incorporates an eductorfluidly communicating with a paint pump, a paint mixing vessel, and apaint return line, thereby providing an improved method of mixing paint.

It should be understood that the preceding is merely a detaileddescription of various embodiments of this invention and that numerouschanges to the disclosed embodiments can be made in accordance with thedisclosure herein without departing from the spirit or scope of theinvention. The preceding description, therefore, exemplifies but shouldnot be construed to limit the scope of the invention.

1. A paint system comprising: at least one paint mixing vesselcontaining paint; at least one pump for circulating a paint stream drawnfrom the mixing vessel; at least one return line for passage of thepaint stream; and at least one eductor in fluid communication with saidat least one paint mixing vessel, and said at least one pump, and saidat least one return line, whereby in operation, paint is pumped throughsaid at least one return line through said at least one eductor, therebydrawing paint from said at least one paint mixing vessel and mixing saidpaint stream within said at least one return line with said drawn paint.2. The paint system of claim 1 further comprising: a second paint mixingvessel containing paint; a second pump for circulating a second paintstream drawn from the second mixing vessel; a second return line forpassage of the second paint stream; and a second eductor in fluidcommunication with said second paint mixing vessel, and said secondpump, and said second return line, whereby in operation, paint is pumpedthrough said second return line through said second eductor, therebydrawing paint from said second paint mixing vessel and mixing saidsecond paint stream with said drawn paint.
 3. The paint system of claim1 further comprising: a plurality of paint mixing vessels, each vesselcontaining paint; a plurality of pumps wherein each pump in saidplurality of pumps corresponds to a respective paint mixing vessel andeach paint mixing vessel corresponds to a respective paint stream, eachof said pumps employed for circulation of said respective paint streamdrawn from each respective mixing vessel; a plurality of return lineswherein each return line corresponds to a respective paint mixing vesselfor passage of a respective paint stream for circulation thereof; and aplurality of eductors wherein each eductor fluidly communicates with acorresponding one of said plurality of return lines, and each eductorfluidly communicates with a corresponding paint mixing vessel, whereinduring operation of said paint system, each eductor draws paint from arespective paint mixing vessel for mixing within a respective paintstream within a respective return line.
 4. A method of mixing paintwithin a paint system, the method comprising the steps of: pumping afirst paint stream from a mixing vessel through the paint system;circulating the paint first paint stream through the system into a firstpaint return line in fluid communication with the mixing vessel; andpassing the first paint stream through an eductor in fluid communicationwith the mixing vessel to draw paint from the mixing vessel and therebymix the drawn paint with paint being circulated in the return line.